Engine synchronization on multi-engine aircraft is known. Existing synchronization methods for dual-spool gas turbine engines typically involve adjusting the rotational speed of a low or high pressure spool of a first engine to substantially match the rotational speed of the corresponding low or high pressure spool of a second engine. Such adjustments can be done via throttle adjustments for the engine on which the rotational speed of the low or high pressure spool is being adjusted. One concern with this method is that it only synchronizes one spool of one engine with one spool of the other engine. Any difference in rotational speeds between the other, unsynchronized spools of each engine is not considered. Depending on its magnitude, the difference in rotational speed between the other unsynchronized spools of the engines can in some situations cause audible noise beats (amplitude modulations) inside of the aircraft cabin. Such noise beats could be unpleasant to aircraft passengers.